1. Field of the Invention
The present invention relates to engine systems having supercharged internal combustion engines having a turbine in the exhaust branch, and relates in particular to a method and a device for operating a wastegate actuator for a wastegate for controlling the exhaust gas enthalpy taken up by the turbine.
2. Description of Related Art
Various systems are known in the related art for controlling or actuating a wastegate on an exhaust gas turbocharger (TC). The wastegate corresponds to a bypass valve in a bypass line bypassing a turbine of the exhaust gas turbocharger. The wastegate is used to convert the exhaust gas enthalpy into a torque of a turbine wheel of the exhaust gas turbocharger and to use the torque to drive a compressor, which provides compressed charge air for an internal combustion engine.
In addition to the conventional pneumatic systems, electric actuators for wastegates, such as e.g. linear actuators, are currently being developed, which are able to provide considerably greater actuating forces. Such linear actuators are connected to a linkage or gearing run out of a housing and are able to displace a cup-type tappet, which opens or closes the wastegate. In such actuators, the forces for holding the open position of the wastegate may reach values in the linkage of up to approximately 250 N. These forces must be provided permanently so as to hold the wastegate e.g. reliably in the closed position such that the wastegate remains sealed.
The electric actuators in the related art have the disadvantage that for the permanent provision of the required closing force of the wastegate they have a high current or energy requirement, which results in a considerable heat loss. Due to the permanent load of a high closing force in the closed state of the wastegate, such actuators have large dimensions and thus also require a large installation space.
It is therefore an objective of the present invention to provide a method, a device and a wastegate actuating system, by which an electrically controlled actuator for a wastegate may be operated in an improved manner, in particular in a more energy-efficient manner. It is furthermore an objective of the present invention to provide an option, in which a higher actuating force is provided at the same power loss as in the related art.